1. Field of the Invention
This invention relates to a novel information processing method and information processing device, which can perform recording and reproduction at high density and high precision, and also can perform erasing of information at high precision.
2. Related Background Art
In recent years, the use of memory materials form the nucleus of electronics industries such as computers and related instruments thereof, video discs, digital audio discs, etc., and developments of their materials have actively progressed. Performances demanded for memory materials, which may differ depending on uses, may be generally as follows: (1) high density and large recording capacity; (2) quick response speed in recording and reproduction; (3) small consumption of power; (4) high productivity and low cost, etc.
In the past, semiconductor memories or magnetic memories employing magnetic materials or semiconductors as the base materials have been predominantly used, but in recent years, with the progress of laser techniques, a recording medium of low cost and high density according to optical memory by use of an organic thin film such as an organic dye, photopolymer is launched into the area.
On the other hand, recently, a scanning tunnel microscope (hereinafter abbreviated as STM) which observes directly the electron structure of the surface atom of a conductor has been developed [G. Binnig et al, Helvetica Physica Acta, 55, 726 (1982)], whereby it has become possible to measure real spatial images of high resolution irrespectively of whether they are single crystalline or amorphous. Besides, it has the advantage that observation can be done at low power without giving damage with current to the medium, and further it can be actuated in air and therefore used for various materials. For such reasons, a wide scope of applications has been expected.
STM utilizes the phenomenon that tunnel current flows when a probe of metal (probe electrode) and an electroconductive substance are approached to a distance of about 1 nm with application of a voltage therebetween. This current is very sensitive to the change in distance between both, and by scanning the probe so as to maintain the tunnel current constant, the surface structure of the real space can be drawn and at the same time various information concerning the whole electron cloud of the surface atoms can be read. In this case, resolution in the interplanar direction is about 1 .ANG.. Accordingly, by applying the principle of STM, it is possible to perform high density recording and reproduction sufficiently at an atomic order (several .ANG.). As the recording and reproduction method in this case, there have been proposed the method in which recording is performed by changing the surface state of an appropriate recording layer by use of a high energy electromagnetic wave such as particulate rays (electron beam, ion beam) or X-ray, etc. and an energy ray such as visible, UV-ray, etc. and reproduction is effected by STM (Japanese Laid-open Patent Application No. 63-204531), or the method in which a material having a memory effect as to the switching characteristics for voltage or current such as a thin film layer of a .pi.-electron type organic compound or a chalcogenide is used as the recording layer, and recording and reproduction are performed by use of STM, etc. (Japanese Laid-open Patent Application Nos. 63-161552, 63-161553).
All of these methods are undoubtedly approaches which enable high density recording which make avail of the characteristics of STM, but such higher densification depends greatly on the scanning precision and the positional control precision of the probe electrode in the interplanar direction of a recording surface (X,Y directions). Presently, a fine movement mechanism of a probe electrode (fine adjustment mechanism) is one utilizing a piezoelectric actuator by use of a piezoelectric element, but there is the problem of hysteresis of a piezoelectric body, which is an obstacle against higher densification of recording. Further, the mechanism of fine adjustment or scanning in the X,Y directions of a probe electrode is not necessarily sufficient generally with respect to perpendicularity of the X-axis and Y-axis. In other words, there is a problem in fine adjustment of the probe electrode or the position reproducibility of the probe electrode during recording and reproduction. As a means for solving such a problem, it may be conceivable to prepare a scale which becomes the standard relative to the position and the direction on the recording medium, detecting the information concerning the position and the direction from such measure, and performing recording and reproduction at the position corresponding to the positional information detected. Such a method has been employed in the recording and reproduction system by VTR, and also in the recording system generally cIassified into the high density recording system in these days, such as an optical disc or optical card. In this case, with accompaniment of higher densification and more fineness of recording, more fine information must be written and detected as a matter of course. As such fine position detecting means, the optical method, the magnetic method or the electrostatic capacity system method can be included, and among them, one which can obtain the highest resolution is the optical method by use of the principle of lattice interference. This permits a monochromatic light to be incident on a diffraction lattice as the standard scale, permits the primary diffracted light diffracted to be synthesized and interfered, converts the obtained light and dark coherent light photoelectrically by a photodetector, and detects the relative deviation amount between the optical system and the standard scale from the lightness and darkness of the coherent light.
However, in the prior art example as mentioned above, the performance (resolving ability) of the lattice interference optical position detection method is determined primarily from the lattice pitch, and it is important how it can be made and detected with good precision, and in the precise working techniques under the present situation (EB pattern drawing or ion beam working), a precision of at most 0.01 .mu.m (=100 .ANG.) is the limit, and also a resolving ability of 0.01 .mu.m is the limit in the detection technique (optical heterodyne method).
Therefore, there has been involved the problem in recording and reproduction by use of STM that precision is markedly inferior and also complicated steps are necessary for lattice preparation.
For this reason, in recording and reproduction by use of STM, there has been made a proposal which utilizes an atomic period based on the regular atomic arrangement within the recording medium plane (Japanese Laid-open Patent Applications Nos. 1-53363 and 1-53364 for tracking). However, concerning the proposal in Japanese Laid-open Patent Application No. 1-53363, the site for detecting the coordinate axis and the site for performing recording and reproduction are different, and the operations at the both sites are performed with one probe, whereby there is involved the problem that the precision of probe control is reflected in the precision of recording and reproduction position detection. On the other hand, concerning the proposal in Japanese Laid-open Patent Application No. 1-53364, there is the problem that the device is complicated, because a probe for detecting the coordinate axis and a probe for performing recording and reproduction are independently necessary.